Sylvain Edward Cappell (born 1946), a Belgian American mathematician and former student of William Browder at Princeton University, is a topologist who has spent most of his career at the Courant Institute of Mathematical Sciences at NYU, where he is now the Silver Professor of Mathematics.

He then graduated from Columbia University in 1966, winning the Van Amringe Mathematical Prize.

[2] He is best known for his "codimension one splitting theorem",[3] which is a standard tool in high-dimensional geometric topology, and a number of important results proven with his collaborator Julius Shaneson (now at the University of Pennsylvania).

Their work includes many results in knot theory (and broad generalizations of that subject)[4] and aspects of low-dimensional topology.

[9] Cappell was elected and served as a vice president of the AMS for the term of February 2010 through January 2013.